sizing pipe threaded elements

guideonl

Hi to everyone,

I have a problem with sizing pipe threaded elements. I am looking for guide rules that with a simple external meassurement I'll be able to determine the element size such as safety valves,threaded pipes,pressure gages,caps etc.
To clarify my question, hereby an example, when I meassure 1/2" safety valve, I can't relate the 1/2" to the actual possible meassurements (ext/int dia) of this valve.
The same problem, when meassuring a threaded hole in a vessele..
I hope that I need not to take several meassurements (ext&int dia, thickness, pitch, number of threads per inch...) and than look at the tables to which size it fits.

Thanks, Guideon

edgepflow

The threads are probably National Pipe Thread Taper (NPT). You can find dimension charts online.

Unrest

I once made a keyring with a set of threads on it, then I could just line them up with whatever I wanted to check.

guideonl

Thanks, Guideon

xxChrisxx

This sort of thing is done by standard. You can use loads of different thread types. NPT are good for about 10k psi if I remember correctly. Above that you'll need to use something different.

Look at a catalogue of someone who sells connetors. So Swagelok, Autoclave engineers, etc.